This invention relates to an acid pickling device for washing and removing oxide scale, formed on the surface of a strip plate, by acid pickling.
FIG. 4 is a perspective side view of a conventional acid pickling device, and FIG. 5 is a sectional view taken on line Vxe2x80x94V in FIG. 4.
In the conventional acid pickling device, as shown in FIGS. 4 and 5, an acid pickling tank 101, which is open upwards, is filled with an acid liquid L for acid pickling of a strip steel plate S. A lid 102 is attached to the top of the acid pickling tank 101 to form an inlet portion 103, and an outlet portion 104. To the inlet portion 103 and the outlet portion 104, aerial deflector rolls 105, 106 and immersion deflector rolls 107, 108 are attached, respectively.
From a lower surface of the lid 102, a hook 109 is suspended. From the hook 109, a ceiling plate 111 is suspended via an engaging stop 110. From the ceiling plate 111, a bottom plate 113 is suspended via connecting plates 112 located at both side parts. On a lower surface of the ceiling plate 111, many immersion guide rolls 115 rotatable via bearing portions 114 are mounted along a direction of travel of the strip steel plate S. On an upper surface of the bottom plate 113, many skids 116 are attached at positions opposed to the immersion guide rolls 115.
Thus, the strip steel plate S is guided by the aerial deflector roll 105 and the immersion deflector roll 107 at the inlet portion 103 into the acid liquid L in the acid pickling tank 101, and travels, while being guided, between the immersion guide rolls 115 and the skids 116. At this time, oxide scale formed on the surface of the strip steel plate S is washed with the acid liquid L and removed thereby. Then, the strip steel plate S is guided by the immersion deflector roll 108 and the aerial deflector roll 106 at the outlet portion 104, and delivered to the outside of the acid pickling tank 101.
Such a conventional acid pickling device is disclosed, for example, in Japanese Unexamined Patent Publication No. 5-78870.
With the foregoing conventional acid pickling device, the acid liquid L is filled into the acid pickling tank 101 which is open upwards, and the lid 102 is attached to the top of the acid pickling tank 101. Thus, the surface area of the acid liquid L in the acid pickling tank 101 is so wide that a loss of acid becomes great as a result of evaporation. Consequently, the washing and removal of the oxide scale on the strip steel plate S by acid pickling are performed insufficiently.
Furthermore, the strip steel plate S travels, while being guided, between the immersion guide rolls 115 and the skids 116 in the acid pickling tank 101. Hence, as the strip steel plate S moves, the acid liquid L follows, and a flow of the acid liquid L toward a downstream side in the direction of travel of the strip steel plate S occurs. This makes the surface of the acid liquid L beside the outlet portion 104 higher, causing an overflow of the acid liquid L from the outlet portion 104 to the outside of the acid pickling tank 101. Besides, the many immersion guide rolls 115 and skids 116 that guide the travel of the strip steel plate S in the acid liquid L are suspended from and supported by the lid 102. Thus, a head weight acts on the lid 102, and may damage it.
The present invention attempts to solve the above problems. Its object is to provide an acid pickling device which suppresses a loss of an acid by decreasing a free surface of an acid liquid in an acid pickling tank, and prevents an overflow to the outside of the tank, thereby making acid pickling of a strip plate efficient.
The present invention is an acid pickling device for acid pickling a strip plate by causing the strip plate to travel in an acid pickling tank filled with an acid liquid while guiding the strip plate by an immersion guide roll and a skid, wherein an acid pickling tank lid for covering a top of the acid pickling tank is disposed such that a central part of the acid pickling tank lid is located at a lower position than a liquid level of the acid liquid in the acid pickling tank to cover a free surface of the acid liquid.
Thus, the surface area of the acid liquid in the acid pickling tank is narrower than in the earlier technology, thereby suppressing the loss of an acid due to evaporation, and ensuring reliable washing and removal of oxide scale on the strip plate by acid pickling. Moreover, the free surface of the acid liquid in the acid pickling tank is forcibly restrained, so that the liquid level of the acid liquid is held constant, thus preventing an overflow of the acid liquid to the outside of the tank. Consequently, the acid pickling of the strip plate can be performed efficiently.
The present invention also concerns the acid pickling device, wherein the immersion guide roll is provided on the acid pickling tank lid, and the skid is provided on a support block installed at the bottom of the acid pickling tank.
Thus, there is no need to suspend heavy materials from the lid, so that the lid can be decreased in rigidity, and can be made light-weight.
The present invention also concerns the acid pickling device, wherein the support block is provided with a bottom plate positioned below the skid and extending along a direction of travel of the strip plate.
Thus, as the strip plate moves in the acid pickling tank, the acid liquid follows, and is flowed downstream in the travel direction. As a result, the acid liquid is circulated, and becomes no more stagnant.
The present invention also concerns the acid pickling device, wherein a plurality of the immersion guide rolls and a plurality of the skids are provided, with predetermined spacing, in a direction of travel of the strip plate, the support block is provided with a bottom plate positioned below the skid and extending along the direction of travel of the strip plate, and the bottom plate is provided with acid liquid passages each located between the adjacent skids.
Thus, as the strip plate moves in the acid pickling tank, the acid liquid follows, generating a flow toward a downstream side in the travel direction. However, the flow of the acid liquid is circulated in the acid pickling tank through the acid liquid passages, thus eliminating stagnation of the acid liquid, and releasing the liquid pressure. Hence, it does not take place that the surface of the acid liquid suddenly becomes high, causing an overflow to the outside of the tank. In addition, the pressure imposed on the lid is also decreased, thus enabling the lid to be decreased in strength and be rendered light-weight.
The present invention also concerns the acid pickling device, wherein the acid liquid passages are each provided between the adjacent skids and upstream in the direction of travel of the strip plate.
Namely, the acid liquid passages are positioned just behind the site of passage of the strip steel plate between the immersion guide rolls and the skids. Thus, the static pressure of the acid liquid on the exit side progressively increases compared with the entrance side for the strip plate in the acid pickling tank. Hence, the acid liquid is agitated, and its circulation can be promoted.
The present invention also concerns the acid pickling device, wherein a plurality of the immersion guide rolls and a plurality of the skids are provided, with predetermined spacing, in a direction of travel of the strip plate, and communication holes for the acid liquid are provided in the support blocks that support the skids.
Thus, as the strip plate moves in the acid pickling tank, the acid liquid follows, generating a flow toward a downstream side in the travel direction. However, the flow of the acid liquid is circulated in the acid pickling tank through the communication holes, thus eliminating stagnation of the acid liquid, and releasing the liquid pressure. Hence, it does not take place that the surface of the acid liquid suddenly becomes high, causing an overflow to the outside of the tank. In addition, the pressure imposed on the lid is also decreased, thus enabling the lid to be decreased in strength and be rendered light-weight.